Project Summary Visual function matures during early life. This maturation is task dependent, and seems to result from changes downstream from primary visual cortex (V1). Unlike V1, the responses of V2 neurons are sensitive to the pres- ence of image statistics like those found in images of natural scenes, their naturalness. This naturalness selectivity can also be seen in downstream areas in the form vision pathway. To better understand how form vi- sion develops, we will use texture naturalness to longitudinally measure behavioral and neuronal development in macaques, recording from areas V1, V2, and IT. The use of a recently-developed target search task enables us to make all measurements in the same animals, and multi-electrode recording methods allow us to sample multiple populations simultaneously. Behaviorally, we will measure how selectivity for texture naturalness develops, how that rate compares to that of contrast sensitivity - measured similarly, and how performance on our search task compares with measurements made in other animals using conventional experimental methods. Physiologically, we will measure how selectivity for naturalness develops in areas V1; V2; and IT, compare how that information is represented - across ages and between areas, and assess how maturational changes in response properties and dynamics affect the encoding of visual information at the neuronal and population levels. Combining the two, we will measure how representations of naturalness in V1, V2, and IT neurons correspond to behavioral selectivity in a task associated with those areas. These experiments will improve our understanding of visual development in primates, and help us understand how neural responses support perception of the visual world.